The present invention relates generally to multimedia files and more specifically to the indexing of information within a multimedia file.
In recent years, the playback of multimedia files has become an integrated part of the average consumer's daily life. Cellular telephones, DVD players, personal computers, and portable media players are all examples of devices that are capable of playing a variety of multimedia files. While each device may be tailored to a particular multimedia format, the extensive proliferation of these devices encourages a certain level of interoperability amongst the different device classes and categories. Likewise, there are certain features such as fast-forward, reverse, start, stop, play, and pause which are expected to behave similarly across all device categories, despite their performance capabilities and use-case application.
One of the most common features of media playback devices is the support for random access, fast-forward and reverse playback of a multimedia file, which is sometimes referred to as “trick play”. Performing trick play functionality generally requires displaying the video presentation at a higher speed in forward and reverse direction, and resuming the overall presentation from a position close to where the viewer terminated the video trick play activity. The audio, subtitle, and other elements of the presentation are typically not used during trick play operations, even though that can be subject to a device's operating preference. In accommodating trick play functionality, multimedia files typically contain an index section used to determine the location of all frames, and specifically the video frames which can be independently decoded and presented to the viewer. When all index information is stored in a single location within a file and linearly references the multimedia information within the file, a player must seek to a specific index entry in order to be able to play a file. For example, a player that is instructed to play a multimedia presentation at the half-way point of the presentation typically processes the first half of the index data before being able to determine the set of data points required to commence playing.
The index section has many other potential applications as well: it may be a necessary element in basic playback of multimedia files that exhibit poor multiplexing characteristics; the index section may also be used to skip over non-essential information in the file; also, an index is often required for the resumption of playback after the termination of trick play functions.